Early diagnosis of pathogenic bacteria and treatment are essential to prevent further infection. Photothermal therapy (PTT) is a promising sterilization method with advantages of minimal invasiveness and high efficiency. The effect of PTT depends on the performance of photothermal materials. Herein, Ti3C2-Au nanomaterials were prepared by the electrostatic self-assembly method, and the absorption characteristics were modulated by changing the morphology of Ti3C2-Au to achieve high photothermal conversion efficiency and sensitive label-free SERS bacterial detection. The results showed that the prepared Ti3C2-Au had better SERS performance than Au and achieved direct and sensitive detection of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Under 808 nm laser irradiation, the photothermal conversion efficiency of Ti3C2-Au nanobipyramids (NBPs) was increased to 50.41% compared with the other two composites. The bactericidal rates of Ti3C2-Au NBPs against E. coli and S. aureus were 95.11 and 99.80% in 8 min, respectively, and the killing rates of nine other bacteria were all above 95%, showing broad-spectrum antibacterial properties. Cell viability studies showed that the Ti3C2-Au NBP had significantly improved biocompatibility compared with the Au NBP and was suitable for biological applications. It can simultaneously realize sensitive bacterial detection and photothermal sterilization and is important for the detection and inhibition of pathogenic bacteria.

Recent years, two-dimensional transition metal carbonitrides (MXene) have attracted much attention in the field of surface-enhanced Raman scattering (SERS). However, the relatively low enhancement of MXene is a major challenge. Herein, Nb2C-Au NPs nanocomposites were prepared by electrostatic self-assembly method, which have a synergistically conjugated SERS effect. The EM hot spots of Nb2C-Au NPs are significantly enlarged and expanded, while the surface Fermi level is decreased. This synergistic effect could improve the SERS performance of the system. Consequently, for the dye molecules CV and MeB, the detection limits reach 10-10 M and 10-9 M, respectively, while for biomolecule adenine, the detection limit is as low as 5 × 10-8 M. The results also show the good concentration-dependent linearity, uniformity, reproducibility and stability of SERS substrate. Nb2C-Au NPs could be a fast, sensitive and stable SERS platform for label-free and non-destructive detection. This work may expand the application of MXene based materials in the field of SERS.

Bacterial infections and the emergence of drug-resistant bacteria threaten human health. Photothermal sterilization has the advantages of temporal and spatial control, no drug resistance, and high efficiency and speed. Photothermal therapy (PTT) causes cell death by means of heat generation. In this work, V2CTx nanosheets are successfully prepared by an improved etching method and the biocompatibility is verified by cytotoxicity. The experiments show that the photothermal properties of V2CTx materials have a significant positive correlation with laser power and material concentration. Only 20 μg/mL of V2CTx can be heated above 70 °C in just 5 min. Photothermal conversion efficiency of V2CTx reaches 45.15% and has good photothermal stability. Taking the typical Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) as experimental bacteria. The results prove that V2CTx itself is a good antibacterial agent, but antibacterial need more than 4 h of culture time. Instead, the photothermal sterilization method shows only 0.125% and 12.72% survival rates for S. aureus and E. coli within 8 min, respectively. Therefore, the prepare V2CTx in this paper only needs 20 μg/mL to achieve efficient photothermal sterilization, which provides a good prospect for clinical treatment of diseases caused by multidrug-resistant bacteria.

The emergence of antibiotic-resistant bacterial strains has caused bacterial infections to become a more serious worldwide health problem. The development of multi-functional platform that can quickly and sensitively detect bacteria and effectively inhibit or kill bacterial is important and urgent. Herein, a novel versatile MXene-Au nanocomposite was successfully synthesized by self-assembly method for rapid detection of bacteria and photothermal sterilization. The typical gram-negative Escherichia coli (E. coli) and the gram-positive Bacillus subtilis (B. subtilis) were used as models to perform label-free, rapid and sensitive detection of bacteria based on SERS method. The antibacterial performance of the material was proved by the colony counting method, and the survival rates of E. coli and B. subtilis were as low as 8.05% and 0.06%, respectively. The Ti3C2Tx-Au nanoparticles (NPs) irradiated with 808 nm light showed significant antibacterial effect within only 6 min, and the germicidal rates for E. coli and B. subtilis were 99.25% and 100%, respectively. The photothermal conversion efficiency reached as high as 43.40%. Accordingly, this multi-functional nanocomposite material can not only detect bacteria sensitively, but also has antibacterial and photothermal sterilization effects, which provides a greatly promising countermeasure for clinical treatment of diseases caused by multi-drug resistant bacteria.